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<head><meta charset="utf-8"><title>sync 2019.06.06 · t-compiler/wg-parallel-rustc · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/index.html">t-compiler/wg-parallel-rustc</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html">sync 2019.06.06</a></h3>

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<a name="167507799"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167507799" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167507799">(Jun 06 2019 at 18:23)</a>:</h4>
<p>Hey <span class="user-mention" data-user-id="220056">@lwshang</span> =)</p>



<a name="167507927"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167507927" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167507927">(Jun 06 2019 at 18:25)</a>:</h4>
<p>I was just reading the 2019.05.24 topic</p>



<a name="167507940"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167507940" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167507940">(Jun 06 2019 at 18:25)</a>:</h4>
<p>I see this comment by <span class="user-mention" data-user-id="116122">@simulacrum</span>:</p>
<blockquote>
<p>we basically want to ask for community feedback on a parallel-enabled compiler and to do so would wants somewhat regular updates of a parallel compiler build</p>
</blockquote>
<p>that seems like a shift from the previous plan, though</p>



<a name="167507960"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167507960" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167507960">(Jun 06 2019 at 18:25)</a>:</h4>
<p>anyway, I'm curious, have we "pulled together" the data that's been gathered so far into one place?</p>



<a name="167508205"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508205" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lwshang <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508205">(Jun 06 2019 at 18:28)</a>:</h4>
<p>Not in <strong>one</strong> place yet. In the meeting minutes, I mentioned there are basically three places we have some data gathered. The hackmd page and two Zulip topics: "Gathering parallel data" and "effect on firefox".</p>



<a name="167508262"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508262" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508262">(Jun 06 2019 at 18:29)</a>:</h4>
<p>OK</p>



<a name="167508264"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508264" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508264">(Jun 06 2019 at 18:29)</a>:</h4>
<p>It seems like it'd be good to try and pull that a bit together</p>



<a name="167508277"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508277" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508277">(Jun 06 2019 at 18:29)</a>:</h4>
<p>I also just left a comment with a few other minor things</p>



<a name="167508313"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508313" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508313">(Jun 06 2019 at 18:29)</a>:</h4>
<blockquote>
<p>that seems like a shift from the previous plan, though</p>
</blockquote>
<p>in particular, this comment was discussing using "alt builds", which would mean that people "opt-in" to the parallel-enabled build.</p>



<a name="167508333"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508333" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508333">(Jun 06 2019 at 18:29)</a>:</h4>
<p>But of course we already use alt builds for another purpose</p>



<a name="167508408"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508408" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508408">(Jun 06 2019 at 18:30)</a>:</h4>
<p>However, that has some appeal, since then they won't experience the seq. overhead</p>



<a name="167508432"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508432" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508432">(Jun 06 2019 at 18:30)</a>:</h4>
<p>One thing I'd like to see is the "whole crate graph" effect of <code>-Zthreads=1</code> for common cases</p>



<a name="167508436"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508436" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508436">(Jun 06 2019 at 18:30)</a>:</h4>
<p>not sure if we've measured that</p>



<a name="167508441"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508441" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508441">(Jun 06 2019 at 18:30)</a>:</h4>
<p>basically our perf results suggested that seq overhead wasn't that bad, but I'm not sure so sure</p>



<a name="167508458"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508458" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508458">(Jun 06 2019 at 18:30)</a>:</h4>
<p>based on the numbers I saw elsewhere...?</p>



<a name="167508470"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508470" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508470">(Jun 06 2019 at 18:31)</a>:</h4>
<p>I'm not sure the best way to organize the data</p>



<a name="167508476"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508476" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508476">(Jun 06 2019 at 18:31)</a>:</h4>
<p>gotta run now tho :)</p>



<a name="167508492"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508492" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> nikomatsakis <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508492">(Jun 06 2019 at 18:31)</a>:</h4>
<p>I'll try to stay on top of this stream a bit more</p>



<a name="167508706"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508706" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lwshang <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508706">(Jun 06 2019 at 18:33)</a>:</h4>
<p>That's great! I'll try to organize data we gathered. And "whole crate graph" is not very clear for me. Could you explain briefly?</p>



<a name="167508995"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167508995" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lwshang <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167508995">(Jun 06 2019 at 18:36)</a>:</h4>
<p><del>When you are back, could you help me to find the discussion about documentation?</del><br>
Just saw your comment in the PR. Will read those sources.</p>



<a name="167511360"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167511360" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167511360">(Jun 06 2019 at 18:58)</a>:</h4>
<p>I think we have whole crate graph at -Zthreads=1</p>



<a name="167511398"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167511398" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167511398">(Jun 06 2019 at 18:58)</a>:</h4>
<p>yeah, the "1" column here <a href="https://docs.google.com/spreadsheets/d/1vadQWQQqTODU1_cAENnUjLyXM6cxms-tiCf2kCiNGGM/edit#gid=0" target="_blank" title="https://docs.google.com/spreadsheets/d/1vadQWQQqTODU1_cAENnUjLyXM6cxms-tiCf2kCiNGGM/edit#gid=0">https://docs.google.com/spreadsheets/d/1vadQWQQqTODU1_cAENnUjLyXM6cxms-tiCf2kCiNGGM/edit#gid=0</a></p>



<a name="167511433"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167511433" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167511433">(Jun 06 2019 at 18:59)</a>:</h4>
<p>0 is a sequential compiler for reference</p>



<a name="167513147"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167513147" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lwshang <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167513147">(Jun 06 2019 at 19:14)</a>:</h4>
<p>That's great. I just recorded the link and explanation in the <a href="https://hackmd.io/KmHulVmISKu7L2HmNgbPgg?view" target="_blank" title="https://hackmd.io/KmHulVmISKu7L2HmNgbPgg?view">hackmd</a> page.</p>



<a name="167513813"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167513813" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167513813">(Jun 06 2019 at 19:21)</a>:</h4>
<p>It's worth noting that data is unique (i.e., not elsewhere on that hackmd)</p>



<a name="167516890"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167516890" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lwshang <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167516890">(Jun 06 2019 at 19:58)</a>:</h4>
<p><span class="user-mention" data-user-id="116122">@simulacrum</span> As quoted in the very beginning of this topic by niko, you said we will ship the parallel-enabled rustc, and gather community feedback on it. I'm wondering what kind of feedback do we want.</p>
<p>Since the user will only have a parallel-enabled rustc in hand, they can't do the comparison between a real single threaded rustc and the parallel-enabled rustc with <code>-Zthreads=1</code>. So that we can't get measurement of the seq overhead from the audience. We may ask the users to compile any rust code with different <code>n</code> in <code>-Zthreads=n</code> and report the difference there. This is currently the only plan in my head. Looking forward to more suggestion.</p>



<a name="167517043"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167517043" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167517043">(Jun 06 2019 at 20:00)</a>:</h4>
<p>so if we want to, we can somewhat easily ship (for a limited set of platforms, e.g. just linux, due to money/CI time budget) ship both parallel and non-parallel compilers to end-users, and make them somewhat readily installable via a shell script or something like that</p>



<a name="167517093"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167517093" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167517093">(Jun 06 2019 at 20:00)</a>:</h4>
<p>(similar to what my script did)</p>



<a name="167517131"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167517131" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167517131">(Jun 06 2019 at 20:00)</a>:</h4>
<p><a href="/user_uploads/4715/u4CfC23udnVU7nNrV92f4Yxj/collect-crategraph-data.sh" target="_blank" title="collect-crategraph-data.sh">collect-crategraph-data.sh</a></p>



<a name="167517163"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167517163" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167517163">(Jun 06 2019 at 20:00)</a>:</h4>
<p>namely the rustup-toolchain-install-master bits</p>



<a name="167517448"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167517448" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lwshang <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167517448">(Jun 06 2019 at 20:04)</a>:</h4>
<p>Wow. Glad to see that opportunity. Niko mentions we did such alt build before. So maybe we can go through a similar approach.</p>



<a name="167517674"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167517674" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167517674">(Jun 06 2019 at 20:06)</a>:</h4>
<p>it doesn't even need to be an alt build -- we can run try builds (or something similar) that just have parallel compiler switched on, that just gets us fewer platforms</p>



<a name="167517737"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167517737" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167517737">(Jun 06 2019 at 20:07)</a>:</h4>
<p>or if we're willing to release somewhat rarely (e.g., just once a week or even just once) we can build a full set of compilers by landing on master and then reverting in the next PR to land</p>



<a name="167518248"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167518248" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lwshang <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167518248">(Jun 06 2019 at 20:14)</a>:</h4>
<p>Yes, that's what I want. Let me elaborate a little bit to make sure we are on the same page.<br>
To do the comparison which shows overhead, the volunteer should have two versions of rustc in hand. They are all latest master branch (aka nightly channel). The only difference is whether <code>parallel-compiler = true or false</code>. </p>
<ul>
<li>During experiment  phase 1 (opt-in), the normal nightly will be <code>parallel-compiler = false</code> and we separately ship a version with <code>parallel-compiler = true</code>.</li>
<li>During phase 2 (opt-out), the normal nightly will be <code>parallel-compiler = true</code> and user can get another version with <code>parallel-compiler = false</code>.</li>
</ul>
<p>Does this look good?</p>



<a name="167518893"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167518893" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167518893">(Jun 06 2019 at 20:21)</a>:</h4>
<p>in theory yes but this wouldn't really be "normal" nightly channel I imagine</p>



<a name="167518908"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167518908" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167518908">(Jun 06 2019 at 20:21)</a>:</h4>
<p>but rather we say, have, one "nightly"-like a week with this sort of split</p>



<a name="167518965"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167518965" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167518965">(Jun 06 2019 at 20:22)</a>:</h4>
<p>but it'll be just rustup-toolchain-install-master installable commits</p>



<a name="167519275"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167519275" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lwshang <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167519275">(Jun 06 2019 at 20:26)</a>:</h4>
<p>My key point is making sure that the only difference between those two versions is <code>parallel-compiler = true or false</code>. Ship it once a week is fine, but nightly are updating every day. Then we must require the user to use a nightly from days before to do the experiment.</p>



<a name="167519438"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167519438" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167519438">(Jun 06 2019 at 20:27)</a>:</h4>
<p>oh, yeah, that would be the only difference</p>



<a name="167519493"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167519493" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167519493">(Jun 06 2019 at 20:28)</a>:</h4>
<p>It's not feasible for us to ship these on a nightly basis or as part of rustup I think though</p>



<a name="167519505"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167519505" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167519505">(Jun 06 2019 at 20:28)</a>:</h4>
<p>so they'd need to be installed somewhat out-of-band</p>



<a name="167519529"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167519529" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lwshang <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167519529">(Jun 06 2019 at 20:28)</a>:</h4>
<p>Will it be pre-compiled?</p>



<a name="167519583"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167519583" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> simulacrum <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167519583">(Jun 06 2019 at 20:29)</a>:</h4>
<p>yeah</p>



<a name="167519690"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/187679-t-compiler/wg-parallel-rustc/topic/sync%202019.06.06/near/167519690" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lwshang <a href="https://rust-lang.github.io/zulip_archive/stream/187679-t-compiler/wg-parallel-rustc/topic/sync.202019.2E06.2E06.html#167519690">(Jun 06 2019 at 20:30)</a>:</h4>
<p>I believe I got all what I want from the side of a general user who may want to join the experiment.</p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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